On her new show Thintervention, celebrity fitness trainer Jackie Warner challenges her overweight clients to change their lifestyles and habits in an attempt to become healthy for life. But losing weight is never easy, not even when Warner is there to shove you along. Warner talks to TIME about her weight-loss regimen, how to eat healthy at a party and why you should never skip meals. (Read about obesity rehab for teens.)

On Thintervention, you tell people, "It's not your fault that you're fat, it's your fault that you're staying that way." What do you mean by that?
The food industry largely conspires to keep America fat. They want to feed us food that gets us fat and keeps us that way. If you follow what they tell you to do, you'll gain weight. So it isn't your fault. But once you have the tips, the tools and the information necessary to take control of your own life  take control of what you ingest  then it's your fault if you knowingly ingest those things and stay fat. If you simply take control, become a good consumer and make smarter choices, then obviously you won't stay fat. The pounds can and will come off.

Some of your clients seem to have no idea that they were unhealthy. What were people's biggest misconceptions of their own lifestyles?
People want a magic pill, a shortcut answer. They look to me and are like, "O.K., fix me. But I don't want to change one aspect of my partying lifestyle or my habit of eating fried foods." That's mistake No. 1. It's hard to lose weight; 25, 30, 50 pounds isn't easy. People need a wake-up call.

What's one major change that they made in order to lose weight?
When I work with morbidly obese clients, I notice there is a similarity between them: they all skip meals. Skipping meals is the No. 1 cause of a slow metabolism. When your metabolism slows, your blood sugar drops and there's a physiological change that occurs. Your insulin drops and your body goes into starvation mode  it purposefully learns to store fat more effectively. The next thing you put in your mouth is almost twice as likely to be stored as fat. I had to work so hard to get people to eat normal meals at normal times.

So is it better to eat small meals throughout the day?
Yes, it's much better. You don't want your insulin to drop, you want it to stay even, which keeps you in a fat-burning zone. You want to be a fat-burning machine, not a fat-storing machine, which is what happens when you don't eat regularly. You can even permanently slow down your metabolism if you skip enough meals. I've seen it many times. I train Hollywood clients and I can't tell you how many times I've seen this. A girl will come in and she's starving herself, eating maybe 800 calories a day. And when she starts eating at regular intervals, she gains weight because she's ruined her metabolism.

Can you fix a slowed metabolism?
Certainly. The best way to do that is through exercise. Obviously the workout burns calories, but exercise also adds muscle to your body. The more muscle you have, the more calories you burn in a day, even while at rest.

You talk a lot about sugar and how bad it is and how you try not to eat above five grams of sugar per day. What is so unhealthy about it?
It's destructive. Sugar makes you stupid: your brain doesn't fire the way it does without sugar. Don't buy fat-free foods because when you take out the fat, you take out the flavor. To get the flavor back, the food industry has probably just added more sugar. It's addictive. And to be clear, we're not talking about candy, cookies and lollipops. Those are bad, of course, but sugar is in virtually every food, from condiments to bread. Crackers, croutons, bread, bagels  that's sugar.

On one episode of Thintervention, one of your clients cheats and eats Oreos. As punishment, you had him hold the Oreos in his hand as he ran up and down the stairs to burn them off. I was surprised at how many stairs it takes to burn off a few cookies.
I think that was one of the most important lessons of the entire series. Look how much effort it takes to burn off two cookies or one Twizzler. People graze at work and at home, and they don't realize the calories are really adding up.

But sometimes, the cookies are right in front of you and it's hard not to take them. Like at holiday parties or when you go out to dinner. What are some tips for staying healthy in those situations?
Never go to a party without eating dinner first. If you know you're going to dinner parties with alcohol, plan ahead and don't drink on other nights when you're not going anywhere. Know yourself, learn what your triggers are going to be.

I also tell people to eat the good, the bad and the ugly. By that I mean, eat the good things on the plate, then the bad things, then the ugly. We usually go to bad and ugly first: the bread and the booze. You want to fill up on lean protein and vegetables. Drink a glass of water, wait a few minutes and then see how you feel and if you want to eat more.